Next generation sequencing panel target genes: possible diagnostic tool for ectodermal dysplasia related diseases

BACKGROUND

Ectodermal dysplasias (EDs) are a large and complex group of disorders affecting the ectoderm-derived organs; the clinical and genetic heterogeneity of these conditions renders an accurate diagnosis more challenging. The aim of this study is to demonstrate the clinical utility of a targeted resequencing panel through enhancing the molecular and clinical diagnosis of EDs. Given the recent developments in gene and protein-based therapies for X-linked hypohidrotic ectodermal dysplasia, there is a re-emerging interest in identifying the genetic basis of EDs and the respective phenotypic presentations, in an aim to facilitate potential treatments for affected families.

METHODS

We assessed seventeen individuals, from three unrelated families, who presented with diverse phenotypes suggestive of ED. An extensive multidisciplinary clinical evaluation was performed followed by a targeted exome resequencing panel (including genes that are known to cause EDs). MiSeqTM data software was used, variants with Qscore >30 were accepted.

RESULTS

Three different previously reported hemizygous EDA mutations were found in the families. However, a complete genotype-phenotype correlation could not be established, neither in our patients nor in the previously reported patients.

CONCLUSIONS

Targeted exome resequencing can provide a rapid and accurate diagnosis of EDs, while further contributing to the existing ED genetic data. Moreover, the identification of the disease-causing mutation in an affected family is crucial for proper genetic counseling and the establishment of a genotype-phenotype correlation which will subsequently provide the affected individuals with a more suitable treatment plan.

Biallelic PRMT7 pathogenic variants are associated with a recognizable syndromic neurodevelopmental disorder with short stature, obesity, and craniofacial and digital abnormalities

PURPOSE

Protein arginine methyltransferase 7 (PRMT7) is a member of a family of enzymes that catalyzes the methylation of arginine residues on several protein substrates. Biallelic pathogenic PRMT7 variants have previously been associated with a syndromic neurodevelopmental disorder characterized by short stature, brachydactyly, intellectual developmental disability, and seizures. To our knowledge, no comprehensive study describes the detailed clinical characteristics of this syndrome. Thus, we aim to delineate the phenotypic spectrum of PRMT7-related disorder.

METHODS

We assembled a cohort of 51 affected individuals from 39 different families, gathering clinical information from 36 newly described affected individuals and reviewing data of 15 individuals from the literature.

RESULTS

The main clinical characteristics of the PRMT7-related syndrome are short stature, mild to severe developmental delay/intellectual disability, hypotonia, brachydactyly, and distinct facial morphology, including bifrontal narrowing, prominent supraorbital ridges, sparse eyebrows, short nose with full/broad nasal tip, thin upper lip, full and everted lower lip, and a prominent or squared-off jaw. Additional variable findings include seizures, obesity, nonspecific magnetic resonance imaging abnormalities, eye abnormalities (i.e., strabismus or nystagmus), and hearing loss.

CONCLUSION

This study further delineates and expands the molecular, phenotypic spectrum and natural history of PRMT7-related syndrome characterized by a neurodevelopmental disorder with skeletal, growth, and endocrine abnormalities.

Identifying phenotypic expansions for congenital diaphragmatic hernia plus (CDH+) using DECIPHER data

Congenital diaphragmatic hernia (CDH) can occur in isolation or in conjunction with other birth defects (CDH+). A molecular etiology can only be identified in a subset of CDH cases. This is due, in part, to an incomplete understanding of the genes that contribute to diaphragm development. Here, we used clinical and molecular data from 36 individuals with CDH+ who are cataloged in the DECIPHER database to identify genes that may play a role in diaphragm development and to discover new phenotypic expansions. Among this group, we identified individuals who carried putatively deleterious sequence or copy number variants affecting CREBBP, SMARCA4, UBA2, and USP9X. The role of these genes in diaphragm development was supported by their expression in the developing mouse diaphragm, their similarity to known CDH genes using data from a previously published and validated machine learning algorithm, and/or the presence of CDH in other individuals with their associated genetic disorders. Our results demonstrate how data from DECIPHER, and other public databases, can be used to identify new phenotypic expansions and suggest that CREBBP, SMARCA4, UBA2, and USP9X play a role in diaphragm development.

8p23.1 deletion: Look out for left ventricular hypertrabeculation and not only congenital heart diseases. Single-center experience and literature revision

Deletions involving the distal portion of the short arm of chromosome 8(8p23.1) show a high phenotypic variability. Congenital heart diseases (CHD) are often described. GATA4 when mutated or deleted is reported to be involved in cardiac morphogenesis. Only twice, left ventricular non compaction (LVNC) was reported in literature in association with 8p23.1 deletion. The present cohort includes five new patients with 8p23.1 deletions including GATA4. The spectrum of CHD is variable. Moreover, in four patients, LV hypertrabeculation was detected and in the fifth LVNC was recognized. Literature revision identified 45 patients with 8p23.1 deletions (encompassing GATA4) and heart involvement. It included wide spectrum of CHD including: heterotaxy spectrum 7/45 (15, 6%), atrioventricular canal 14/45 (balanced 3/45 including two of them with hypoplastic aortic arch; unbalanced 4/45, Fallot-AVC 1/45, partial AVC 3/45, unspecified 3/45), predominant major left heart lesions included 2/45 (4, 4%): interrupted aortic arch and hypoplastic left heart syndrome. Left ventricular hypertrabeculation might be potentially underestimated in patients with 8p23.1 deletion. These might suggest the importance of including microarray analysis in this group of patients. Moreover, 8p23.1 microdeletion or GATA4 variants can be considered in heterotaxy genetic panels.

Congenital heart defects in the recurrent 2q13 deletion syndrome

The recurrent 2q13 deletion syndrome is a rare genetic disorder associated with developmental delay, cardiac and urogenital malformations, and minor facial anomalies. Congenital heart defects (CHDs) are the most frequent malformations associated with del2q13. Experimental studies in zebrafish suggest that two genes mapping within the 2q13 critical region (FBLN7 and TMEM87B) could confer susceptibility to congenital heart defects in affected individuals. We reviewed the cardiac characteristics in four patients with 2q13 deletion admitted to our hospitals, and in published patients. Two of our patients had congenital heart defects, consisting in partial anomalous pulmonary venous connection, ostium secundum atrial septal defect ostium secundum, and small muscular ventricular septal defect in one of them, and aortic valve insufficiency with partial fusion of two commissures (incomplete bicuspid aortic valve) and mitral valve insufficiency due to trivial mitral valve prolapse in the other. The anatomic types of CHD in del2q13 syndrome are highly variable and distributed widely, including laterality defects, complex atrioventricular septal defect, septal anomalies, and cardiomyopathies. Cardiac evaluation should be part of the clinical workup at diagnosis of 2q13 deletion.

Genetic contributors to risk of schizophrenia in the presence of a 22q11.2 deletion

Schizophrenia occurs in about one in four individuals with 22q11.2 deletion syndrome (22q11.2DS). The aim of this International Brain and Behavior 22q11.2DS Consortium (IBBC) study was to identify genetic factors that contribute to schizophrenia, in addition to the ~20-fold increased risk conveyed by the 22q11.2 deletion. Using whole-genome sequencing data from 519 unrelated individuals with 22q11.2DS, we conducted genome-wide comparisons of common and rare variants between those with schizophrenia and those with no psychotic disorder at age ≥25 years. Available microarray data enabled direct comparison of polygenic risk for schizophrenia between 22q11.2DS and independent population samples with no 22q11.2 deletion, with and without schizophrenia (total n = 35,182). Polygenic risk for schizophrenia within 22q11.2DS was significantly greater for those with schizophrenia (padj = 6.73 × 10-6). Novel reciprocal case-control comparisons between the 22q11.2DS and population-based cohorts showed that polygenic risk score was significantly greater in individuals with psychotic illness, regardless of the presence of the 22q11.2 deletion. Within the 22q11.2DS cohort, results of gene-set analyses showed some support for rare variants affecting synaptic genes. No common or rare variants within the 22q11.2 deletion region were significantly associated with schizophrenia. These findings suggest that in addition to the deletion conferring a greatly increased risk to schizophrenia, the risk is higher when the 22q11.2 deletion and common polygenic risk factors that contribute to schizophrenia in the general population are both present.

Atypical cardiac defects in patients with RASopathies: Updated data on CARNET study

BACKGROUND

RASopathies are a set of relatively common autosomal dominant clinically and genetically heterogeneous disorders. Cardiac outcomes in terms of mortality and morbidity for common heart defects (such as pulmonary valve stenosis and hypertrophic cardiomyopathy) have been reported. Nevertheless, also Atypical Cardiac Defects (ACDs) are described. The aim of the present study was to report both prevalence and cardiac outcome of ACDs in patients with RASopathies.

METHODS

A retrospective, multicentric observational study (CArdiac Rasopathy NETwork-CARNET study) was carried out. Clinical, surgical, and genetic data of the patients who were followed until December 2019 were collected.

RESULTS

Forty-five patients out of 440 followed in CARNET centers had ACDs. Noonan Syndrome (NS), NS Multiple Lentigines (NSML) and CardioFacioCutaneous Syndrome (CFCS) were present in 36, 5 and 4 patients, respectively. Median age at last follow-up was 20.1 years (range 6.9-47 years). Different ACDs were reported, including mitral and aortic valve dysfunction, ascending and descending aortic arch anomalies, coronary arteries dilation, enlargement of left atrial appendage and isolated pulmonary branches diseases. Five patients (11%) underwent cardiac surgery and one of them underwent a second intervention for mitral valve replacement and severe pericardial effusion. No patients died in our cohort until December 2019.

CONCLUSIONS

Patients with RASopathies present a distinct CHD spectrum. Present data suggest that also ACDs must be carefully investigated for their possible impact on the clinical outcome. A careful longitudinal follow up until the individuals reach an adult age is recommended.

Smith-Magenis syndrome: Report of morphological and new functional cardiac findings with review of the literature

Smith-Magenis syndrome (SMS) is a genetic disorder characterized by multiple congenital anomalies, sleep disturbance, behavioral impairment, and intellectual disability. Its genetic cause has been defined as an alteration in the Retinoic Acid-Induced 1 gene. Cardiac anomalies have been reported since the first description of this condition in patients with 17p11.2 deletion. Variable cardiac defects, including ventricular septal defects, atrial septal defects, tricuspid stenosis, mitral stenosis, tricuspid and mitral regurgitation, aortic stenosis, pulmonary stenosis, mitral valve prolapse, tetralogy of Fallot, and total anomalous pulmonary venous connection, have been anecdotally reported and systematic case series are still lacking. Herein, we define the spectrum of the cardiac phenotype and describe for the first time the cardiac function in a large cohort of pediatric patients with SMS. Revision of the literature and correlations between genotype and cardiac phenotype was performed.

Biallelic hypomorphic variants in ALDH1A2 cause a novel lethal human multiple congenital anomaly syndrome encompassing diaphragmatic, pulmonary, and cardiovascular defects

This study shows a causal association between ALDH1A2 variants and a novel, severe multiple congenital anomaly syndrome in humans that is neonatally lethal due to associated pulmonary hypoplasia and respiratory failure. In two families, exome sequencing identified compound heterozygous missense variants in ALDH1A2. ALDH1A2 is involved in the conversion of retinol (vitamin A) into retinoic acid (RA), which is an essential regulator of diaphragm and cardiovascular formation during embryogenesis. Reduced RA causes cardiovascular, diaphragmatic, and associated pulmonary defects in several animal models, matching the phenotype observed in our patients. In silico protein modeling showed probable impairment of ALDH1A2 for three of the four substitutions. In vitro studies show a reduction of RA. Few pathogenic variants in genes encoding components of the retinoic signaling pathway have been described to date, likely due to embryonic lethality. Thus, this study contributes significantly to knowledge of the role of this pathway in human diaphragm and cardiovascular development and disease. Some clinical features in our patients are also observed in Fryns syndrome (MIM# 229850), syndromic microphthalmia 9 (MIM# 601186), and DiGeorge syndrome (MIM# 188400). Patients with similar clinical features who are genetically undiagnosed should be tested for recessive ALDH1A2-deficient malformation syndrome.

Comparison of Adaptive Functioning in Children with Williams Beuren Syndrome and Autism Spectrum Disorder: A Cross-Syndrome Study

Williams Beuren syndrome (WBS) and autism spectrum disorder (ASD) have been long considered as "polar opposite" disorders. Although children with WBS appears to be hypersociable, recent researches have revealed difficulties in socio-communicative skills such as shared attention, showing or giving objects, social relationships comprehension, pragmatic use of language, and emotion's recognition. The aim of this cross-syndrome study is to compare clinician-report adaptive profiles of two wide developmental range children by means of Vineland Adaptive Behavior Scales-Interview Edition, Survey Form. Eighty individuals, 40 with WBS and 40 with ASD (31 preschoolers and 49 scholars) with ASD and WBS matched for chronological age and developmental/cognitive level were recruited. Analysis of domains and subdomains have been reported. Results showed no significant difference in global adaptive level between WBS and ASD in both preschooler and scholar children. Communication domain significantly differ in preschoolers (higher in WBS children), but not in scholars. Expressive subdomain significantly differ in both preschoolers and scholars (higher in WBS children). Play and Leisure subdomain significantly differ in scholars (higher in WBS children), but not in preschoolers. Our results support hypothesis on a shared global adaptive impairment in children with WBS and ASD, by extending this findings to scholar-age children. Analysis of domains and subdomains differences highlight the need for interventions targeting social-pragmatic skills since first years of life. Differences in preschoolers and scholars adaptive profiles could be explained through a developmental perspective. LAY SUMMARY: Little is known about differences in adaptive profiles between Williams Beuren syndrome and autism spectrum disorder. Our results show similarities in global adaptive level and difference in communication level. Furthermore, expressive skills seem to be higher in Williams Beuren Syndrome. Autism Res 2021, 14: 748-758. © 2020 International Society for Autism Research and Wiley Periodicals LLC.

Microcephalic osteodysplastic primordial dwarfism type II and pachygyria: Morphometric analysis in a 2-year-old girl

Microcephalic osteodysplastic primordial dwarfism (MOPD) type II is a rare disorder characterized by skeletal dysplasia, severe proportionate short stature, insulin resistance and cerebrovascular abnormalities including cerebral aneurysms and moyamoya disease. MOPD type II is caused by mutations in the pericentrin (PCNT) gene, which encodes a protein involved in centrosomes function. We report a 2 year old girl affected by MOPD type II caused by two compound heterozygous loss-of-function variants in PCNT gene, of which one is a novel variant (c.5304delT; p.Gly1769AlafsTer34). The patient presented atypical brain magnetic resonance imaging (MRI) findings consistent with pachygyria. This was confirmed by morphometric analysis of cortical thickness (CT) and gyrification index by comparing MRI data of the patient with a group of eight age-matched healthy controls. The statistical analysis revealed a significant and diffuse increase of CT with an anterior-predominant pattern and diffuse reduced gyrification (p < .05). These findings provide new evidences to the emergent concept that malformations of cortical development are complex disorders and that new genetic findings contribute to the fading of classification borders.

TUBB3 E410K syndrome: Case report and review of the clinical spectrum of TUBB3 mutations

The tubulinopathies refer to a wide range of brain malformations caused by mutations in one of the seven genes encoding different tubulin's isotypes. The β-tubulin isotype III (TUBB3) gene has a primary function in nervous system development and axon generation and maintenance, due to its neuron-specific expression pattern. A recurrent heterozygous mutation, c.1228G > A; p.E410K, in TUBB3 gene is responsible of a rare disorder clinically characterized by congenital fibrosis of the extraocular muscle type 3 (CFEOM3), intellectual disability and a wide range of neurological and endocrine abnormalities. Other mutations have been described spanning the entire gene and genotype-phenotype correlations have been proposed. We report on a 3-year-old boy in whom clinical exome sequencing allowed to identify a de novo TUBB3 E410K mutation as the molecular cause underlying a complex phenotype characterized by a severe bilateral palpebral ptosis refractory to eye surgery, psychomotor delay, absent speech, hypogonadism, celiac disease, and cyclic vomiting. Brain MRI revealed thinning of the corpus callosum with no evidence of malformation cortical dysplasia. We reviewed available records of patients with TUBB3 E410K mutation and compared their phenotype with the clinical outcome of patients with other mutations in TUBB3 gene. The present study confirms that TUBB3 E410K results in a clinically recognizable phenotype, unassociated to the distinct cortical dysplasia caused by other mutations in the same gene. Early molecular characterization of TUBB3 E410K syndrome is critical for targeted genetic counseling and prompt prospective care in term of neurological, ophthalmological, endocrine, and gastrointestinal follow-up.

Defining language disorders in children and adolescents with Noonan Syndrome

Background

Noonan Syndrome is a developmental disorder characterized by a distinctive phenotype including facial dysmorphism, webbed neck, short stature, heart defects, and variable cognitive deficits as major features. Over the years, neuropsychological and behavioral studies explored alteration of cognitive functioning and related domains, such as learning, memory, and attention. To our knowledge, however, data concerning the language profile in this disorder is scarce. The aim of the present study was to detect specific language functioning combining nonverbal intelligence quotient and language abilities and to pinpoint strengths and weaknesses in the language domains.

Methods

The language profile of 37 Italian participants with molecularly confirmed diagnosis of Noonan Syndrome was evaluated using specific tools to assess vocabulary and grammar comprehension and production, as well as phonological development.

Results

We observed that 78% of affected individuals exhibited language impairment. Within language domains, the strong area was lexical production and grammar production was the weak area. Almost half the participants manifested a similar trend of specific language impairment. Nonverbal intelligence quotient only correlated with grammar comprehension.

Conclusion

Our study expands present knowledge about the language profile in NS, and provides data that could enable more effective patient management and appropriate intervention.

Clinical spectrum of individuals with pathogenic NF1 missense variants affecting p.Met1149, p.Arg1276, and p.Lys1423: genotype-phenotype study in neurofibromatosis type 1

We report 281 individuals carrying a pathogenic recurrent NF1 missense variant at p.Met1149, p.Arg1276, or p.Lys1423, representing three nontruncating NF1 hotspots in the University of Alabama at Birmingham (UAB) cohort, together identified in 1.8% of unrelated NF1 individuals. About 25% (95% confidence interval: 20.5-31.2%) of individuals heterozygous for a pathogenic NF1 p.Met1149, p.Arg1276, or p.Lys1423 missense variant had a Noonan-like phenotype, which is significantly more compared with the "classic" NF1-affected cohorts (all p < .0001). Furthermore, p.Arg1276 and p.Lys1423 pathogenic missense variants were associated with a high prevalence of cardiovascular abnormalities, including pulmonic stenosis (all p < .0001), while p.Arg1276 variants had a high prevalence of symptomatic spinal neurofibromas (p < .0001) compared with "classic" NF1-affected cohorts. However, p.Met1149-positive individuals had a mild phenotype, characterized mainly by pigmentary manifestations without externally visible plexiform neurofibromas, symptomatic spinal neurofibromas or symptomatic optic pathway gliomas. As up to 0.4% of unrelated individuals in the UAB cohort carries a p.Met1149 missense variant, this finding will contribute to more accurate stratification of a significant number of NF1 individuals. Although clinically relevant genotype-phenotype correlations are rare in NF1, each affecting only a small percentage of individuals, together they impact counseling and management of a significant number of the NF1 population.

SOS1 mutations in Noonan syndrome: Cardiomyopathies and not only congenital heart defects! Report of six patients including two novel variants and literature review

Noonan syndrome (NS) is caused by mutations in more than 10 genes, mainly PTPN11, SOS1, RAF1, and RIT1. Congenital heart defects and cardiomyopathy (CMP) are associated with significant morbidity and mortality in NS. Although hypertrophic CMP has "classically" been reported in association to RAF1, RIT1, and PTPN11 variants, SOS1 appears to be poorly related to CMP. Patients with NS attending our Center from January 2013 to June 2018 were eligible for inclusion if they carried SOS1 variants and presented with-or developed-CMP. Literature review describing the co-existence of SOS1 mutation and CMP was also performed. We identified six patients with SOS1 variants and CMP (male to female ratio 2:1) including two novel variants. CMP spectrum encompassed: (a) dilated CMP, (b) nonobstructive hypertrophic CMPs, and (c) obstructive hypertrophic CMPs. Survival is 100%. Literature review included 16 SOS1 mutated in CMP. CMP, mainly hypertrophic, has been often reported in association to RAF1, RIT1, and PTPN11 variants. Differently from previous reports, due to the frequent association of SOS1 variants and CMP in our single center experience, we suggest potential underestimated proportion of SOS1 in pediatric CMPs.

Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation

PURPOSE

Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors.

METHODS

A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study.

RESULTS

None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_2972del.

CONCLUSION

We demonstrate that individuals with the NF1 p.Met992del pathogenic variant have a mild NF1 phenotype lacking clinically suspected plexiform, cutaneous, or subcutaneous neurofibromas. However, learning difficulties are clearly part of the phenotypic presentation in these individuals and will require specialized care.

Correction: Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation

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First Report of Low-Rate Mosaicism for 20q11.21q12 Deletion and Delineation of the Associated Disorder

Interstitial deletions of the long arm of chromosome 20 are very rare, with only 12 reported patients harboring the 20q11.2 microdeletion and presenting a disorder characterized by psychomotor and growth delay, dysmorphisms, and brachy-/clinodactyly. We describe the first case of mosaic 20q11.2 deletion in a 5-year-old girl affected by mild psychomotor delay, feeding difficulties, growth retardation, craniofacial dysmorphisms, and finger anomalies. SNP array analysis disclosed 20% of cells with a 20q11.21q12 deletion, encompassing the 20q11.2 minimal critical region and the 3 OMIM disease-causing genes GDF5, EPB41L1, and SAMHD1. We propose a pathogenic role of other genes mapping outside the small region of overlap, in particular GHRH (growth hormone releasing hormone), whose haploinsufficiency could be responsible for the prenatal onset of growth retardation which is shared by half of these patients. Our patient highlights the utility of chromosomal microarray analysis to identify low-level mosaicism.

Cardiovascular disease in Down syndrome

PURPOSE OF REVIEW

In the last 40 years, with a better understanding of cardiac defects, and with the improved results of cardiac surgery, the life expectancy of persons with Down syndrome has significantly increased. This review article reports on advances in knowledge of cardiac defects and cardiovascular system of persons with trisomy 21.

RECENT FINDINGS

New insights into the genetics of this syndrome have improved our understanding of the pathogenetic mechanisms of cardiac defects. Recent changes in neonatal prevalence of Down syndrome suggest a growing number of children with cardiac malformations, in particular with simple types of defects. Ethnic and sex differences of the prevalence of specific types of congenital heart disease (CHD) have also been underlined. A recent study confirmed that subclinical morphologic anomalies are present in children with trisomy 21, also in the absence of cardiac defects, representing an internal stigma of Down syndrome. The results of cardiac surgery are significantly improved in terms of immediate and long-term outcomes, but specific treatments are indicated in relation to pulmonary hypertension. Particular aspects of the cardiovascular system have been described, clarifying a reduced sympathetic response to stress but also a 'protection' from atherosclerosis and arterial hypertension in these patients.

SUMMARY

Continuing dedication to clinical and basic research studies is essential to further improve survival and the quality of life from childhood to adulthood of patients with trisomy 21.

Small 4p16.3 deletions: Three additional patients and review of the literature

Wolf-Hirschhorn syndrome is a well-defined disorder due to 4p16.3 deletion, characterized by distinct facial features, intellectual disability, prenatal and postnatal growth retardation, and seizures. Genotype-phenotype correlations based on differently sized deletions have been attempted, and some candidate genes have been suggested. We report on clinical characteristics of three patients with pure interstitial submicroscopic 4p16.3 deletions, ranging in size from 68 to 166 kb, involving WHSCR1 and/or part of WHSCR2, and review published cases with overlapping 4p16.3 losses. The present study highlights a major role of NSD2 gene in the pathogenesis of the WHS main features and predicts that loss-of-function mutations affecting NSD2 gene could result in microcephaly, prenatal and postnatal growth retardation, psychomotor and language delay, and craniofacial features. Absent seizures in all subjects corroborate the suggestion that this specific feature is causally linked with at least one additional causative gene. Finally, we suggest that mir-943 could play a role in the pathogenesis of CHD in some of these patients.

Atrioventricular canal defect and genetic syndromes: The unifying role of sonic hedgehog

The atrioventricular canal defect (AVCD) is a congenital heart defect (CHD) frequently associated with extracardiac anomalies (75%). Previous observations from a personal series of patients with AVCD and "polydactyly syndromes" showed that the distinct morphology and combination of AVCD features in some of these syndromes is reminiscent of the cardiac phenotype found in heterotaxy, a malformation complex previously associated with functional cilia abnormalities and aberrant Hedgehog (Hh) signaling. Hh signaling coordinates multiple aspects of left-right lateralization and cardiovascular growth. Being active at the venous pole the secondary heart field (SHF) is essential for normal development of dorsal mesenchymal protrusion and AVCD formation and septation. Experimental data show that perturbations of different components of the Hh pathway can lead to developmental errors presenting with partially overlapping manifestations and AVCD as a common denominator. We review the potential role of Hh signaling in the pathogenesis of AVCD in different genetic disorders. AVCD can be viewed as part of a "developmental field," according to the concept that malformations can be due to defects in signal transduction cascades or pathways, as morphogenetic units which may be altered by Mendelian mutations, aneuploidies, and environmental causes.

Expanding the clinical and molecular spectrum of PRMT7 mutations: 3 additional patients and review

Protein arginine methyltransferase 7 (PRMT7) is a member of a family of enzymes that catalyze the transfer of methyl groups from S-adenosyl-l-methionine to nitrogen atoms on arginine residues. Arginine methylation is involved in multiple biological processes, such as signal transduction, mRNA splicing, transcriptional control, DNA repair, and protein translocation. Currently, 7 patients have been described harboring compound heterozygous or homozygous variants in the PRMT7 gene, causing a novel intellectual disability syndrome, known as SBIDDS syndrome (Short Stature, Brachydactyly, Intellectual Developmental Disability, and Seizures). We report on 3 additional patients from 2 consanguineous families with severe/moderate intellectual disability, short stature, brachydactyly and dysmorphisms. Exome sequencing revealed 2 novel homozygous mutations in PRMT7. Our findings expand the clinical and molecular spectrum of homozygous PRMT7 mutations, associated to the SBIDDS syndrome, showing a possible correlation between the type of mutation and the severity of the phenotype.